Modern vehicle concepts and structural designs of vehicles have a plurality of cavities which have to be sealed in order to prevent the ingress of moisture and contaminants, since the latter can result in corrosion from the inside on the corresponding body parts. This applies, in particular, to modern self-supporting body constructions in which a heavy frame construction is replaced by so-called “space frames”. With the latter, use is made of a lightweight, structurally solid chassis made of prefabricated hollow sections. Such constructions have, depending upon the specific system, a number of cavities which have to be sealed against the penetration of moisture and contaminants. These cavities include the upwardly extending A-, B- and C-pillars supporting the roof structure, the roof rail, portions of the fenders, or the sill. In addition, these cavities transmit airborne sound in the form of unpleasant vehicle running noises and wind noises, therefore such sealing measures also serve to reduce the noises and therefore to enhance the comfort of traveling in the vehicle. During the assembly of the car, these frame parts and body parts containing cavities are prefabricated from half-shell components which were joined at a later time by welding and/or adhesive bonding so as to form the closed hollow section. With such a type of construction the cavity in the early body in white (“body shop”) state of a vehicle body is accordingly easily accessible, so that sealing and acoustically damping baffle parts (sometimes referred to as “pillar fillers” or “cavity filler inserts”) can be fixed in this early phase of body construction by mechanical hanging, by insertion into appropriate holding devices, bores or by welding to the cavity walls.
Most modern baffles are designed to include a sealing material disposed on a support member or carrier. The carrier is generally manufactured from a rigid material, such as hard plastic, such that its shape approximates the shape of the cavity to be sealed. The carrier/sealing material combination is configured such that the carrier is inserted into a cavity, and the sealing material creates an airtight seal between the carrier and the walls of the cavity. Typically, the sealing material is activated (thermally or chemically) after insertion into the cavity so that the sealing material forms a seal with the walls of the cavity.
DE 3838655 A1 discloses a method for acoustic insulation of vehicle body cavities by using a commercially available polyurethane foam material which is to be saturated with an tacky plastic compound, so that after manual compression it bonds together briefly before re-expanding. This reference suggests to provide a bore in the cavity wall into a which a sleeve is being inserted. The continuation of this sleeve has sections which can swing open to form an outlet opening for the foam to expand into the cavity.
From WO 99/37506 a cavity sealing article is known which comprises a planar support member and a sealing member comprising a foamable polymer which surrounds in an intimate contact the support member and which is in plane with the support member. The foamable polymer comprises at least two layers which are in intimate contact and which are in the plane of the support member. The outer most layer of the sealing member comprises an uncross linked foamable polymer and the inner layer comprises a cross linked foamable polymer.
WO 00/03894 A1 discloses a lightweight expandable baffle for sealing a cavity of a vehicle body at a predetermined cross section of the cavity. This baffle includes a rigid support plate having an outer periphery with a shape generally corresponding to but smaller than the shape of the cross section of the cavity. Said baffle comprises a heat expandable sealing material mounted to the outer periphery of the rigid support plate having an activation temperature range at which the material expands. The support plate is being formed of a material having a higher melting point than the activation temperature range of the sealing material. When activated, the sealing material expands radially from the rigid support plate to fill the cross-sectional cavity between the rigid support plate and the cavity walls.
WO 01/83206 A1 discloses a combined baffle and reinforcing assembly for use within the cavity of a structural member to dampen acoustic transmissions through the cavity and to provide reinforcement in a direction transverse to the longitudinal axis of the structural member. The combined assembly includes a synthetic carrier which comprises an interior area, a marginal rim and an attachment member preferably in a form of a clip suited for insertion to the corresponding hole in the wall of the structural member. The carrier is circumscribed by a continuous band of reinforcing material extending around the periphery of the carrier. The marginal rim of the carrier may include a base wall and a support flange for receiving the thermally expandable material thereon.
WO 01/71225 describes an expandable baffle part for sealing cavities in automobiles. This part comprises a thermally expandable sealing material that is able to expand at the temperatures of the E-coat bake oven. Moreover, the baffle part comprises a support which positions and fixes the expandable material at the predetermined point in the cavity until the thermal expansion sets in. The support further has at least one clip or a snap-action or plug-in device which is inserted under pressure into a corresponding bore or aperture in the hollow-space structure in order to fix the component.
WO 03/004314 discloses a sound insulation device for mounting in a tubular part, in particular a motor vehicle body work part. This insulation device comprises a partitioning insert, a cord of a composition that is thermally expandable to form a foam, whereby the cord is fitted to the periphery of the insert. The device further comprises retaining means for holding the cord on the insert prior to expansion of the cord and means for encouraging the cord to expand towards the inside wall of the tubular part. It is suggested that the cord is formed by being extruded in rectilinear manner without any particular shaping and wherein the cord retaining means are integrally molded with the partitioning insert and also serve to shape the extruded cord around the periphery of the partitioning insert.
WO 2005/037608 A1 refers to an acoustic baffle for use in a cavity in a structural member. The baffle comprises a double walled support member, whereby the first wall is spaced a part from the second wall to define an acoustical gap of the predetermined dimensions between the two walls of the support member. An expandable sealing material is coupled with supported by at least apportion of the support member of the baffle to provide a localized sealing and sound separation to frames, rails, cavities, panels and other structural members of an automotive vehicle body.
JP2004-252169A discloses a sealing device for hollow structures with intricate sectional shape. The device comprises a first holder plate formed in correspondence to the cross sectional shape of the cavity of the hollow structure and a second holder plate holding a foamable base material between itself and the first plate. Only the one side face of the foamable base material is supported by the first plate in approximately the central region of the hollow chamber. Both side faces of the foamable base material are held by the first and the second plate and in a projected region which projects on the upper left of the peripheral edge of the hollow chamber.
US2006/0041227 A1 discloses a blocking device for mounting a blocking member and a fixing device within a space defined within a hollow structure of a car body. The blocking member may be disposed on one side of a wall portion extending within the space. The blocking member has an expandable member and a holder for holding the expandable member. The expandable member is expandable by heat to form a foam member. The fixing device has a fixing member that may be disposed on the other side of the wall portion within the space. The fixing device also has a connecting member that may extend through an insertion hole formed in the wall portion. The connecting member connects the blocking member to the fixing member.
While the above mentioned baffles have been successfully employed to seal automotive body cavities against the intrusion of dust, water, carbon monoxide and to a certain extent noise, a need exists for an improved baffle with enhanced sound suppression capability which can be manufactured in a simple and cost effective process.